I know what you mean! Somehow Fragmentarium is not yet handling inside lighting very well. Maybe the fractal insides are not that interesting to the programmers yet? We must lobby!
When DE-tracers gone to 3D light position, insides of fractal becomes in shaded area (like real world). And there is no any interference of light. So scenes without directional light will looks better on GI
Still have to try GI! All kind of things got in the way, like 5 days in Berlin unexpectedly and family birthdays etc etc:} So: a lot of nice things to explore in free time now